Question

我有一个问题是如何从多列中获取所有MIN / MAX值的所有日期以及如何优化它。我已经试着让它在很长一段时间内合理运行，我几乎放弃了： - （

数据库存储来自各种设备的大量温度。并以这种方式构建。

ID, User, DateTime, Temp1, Temp2, Temp3 and so on.

现在我想提取每个测量的MIN和MAX的所有日期和值（MIN Temp1的日期，MAX Temp1的日期......）

获得MIN / MAX值非常简单快捷。

SELECT
MIN(Modul_FremL) as Min_Temp1,
MAX(Modul_FremL) as Max_Temp1,
MIN(Modul_ReturL) as Min_Temp2,
MAX(Modul_ReturL) as Max_Temp2,
MIN(Modul_Gas) as Min_Temp3,
MAX(Modul_Gas) as Max_Temp3,
MIN(Modul_FB) as Min_Temp4,
MAX(Modul_FB) as Max_Temp4,
MIN(Modul_SB) as Min_Temp5,
MAX(Modul_SB) as Max_Temp5,
MIN(Temp_Kedel) as Min_Temp6,
MAX(Temp_Kedel) as Max_Temp6,
MIN(Temp_Central) as Min_Temp7,
MAX(Temp_Central) as Max_Temp7,
MIN(Temp_VVB) as Min_Temp8,
MAX(Temp_VVB) as Max_Temp8,
MIN(Temp_Ude) as Min_Temp9,
MAX(Temp_Ude) as Max_Temp9
FROM pillestat_data_1
LIMIT 1

仅获取此数据从数据库中获取超过300,000行的所有数据只需0.2004秒。

但是我还需要MIN / MAX的日期时间，我试过这个。

SELECT DatoTid, MIN(Modul_FremL) as Temperatur FROM pillestat_data_1 WHERE Modul_FremL = (SELECT MIN(Modul_FremL) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Modul_FremL) as Temperatur FROM pillestat_data_1 WHERE Modul_FremL = (SELECT MAX(Modul_FremL) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Modul_ReturL) as Temperatur FROM pillestat_data_1 WHERE Modul_ReturL = (SELECT MIN(Modul_ReturL) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Modul_ReturL) as Temperatur FROM pillestat_data_1 WHERE Modul_ReturL = (SELECT MAX(Modul_ReturL) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Modul_Gas) as Temperatur FROM pillestat_data_1 WHERE Modul_Gas = (SELECT MIN(Modul_Gas) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Modul_Gas) as Temperatur FROM pillestat_data_1 WHERE Modul_Gas = (SELECT MAX(Modul_Gas) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Modul_FB) as Temperatur FROM pillestat_data_1 WHERE Modul_FB = (SELECT MIN(Modul_FB) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Modul_FB) as Temperatur FROM pillestat_data_1 WHERE Modul_FB = (SELECT MAX(Modul_FB) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Modul_SB) as Temperatur FROM pillestat_data_1 WHERE Modul_SB = (SELECT MIN(Modul_SB) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Modul_SB) as Temperatur FROM pillestat_data_1 WHERE Modul_SB = (SELECT MAX(Modul_SB) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Temp_Kedel) as Temperatur FROM pillestat_data_1 WHERE Temp_Kedel = (SELECT MIN(Temp_Kedel) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Temp_Kedel) as Temperatur FROM pillestat_data_1 WHERE Temp_Kedel = (SELECT MAX(Temp_Kedel) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Temp_Central) as Temperatur FROM pillestat_data_1 WHERE Temp_Central = (SELECT MIN(Temp_Central) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Temp_Central) as Temperatur FROM pillestat_data_1 WHERE Temp_Central = (SELECT MAX(Temp_Central) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Temp_VVB) as Temperatur FROM pillestat_data_1 WHERE Temp_VVB = (SELECT MIN(Temp_VVB) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Temp_VVB) as Temperatur FROM pillestat_data_1 WHERE Temp_VVB = (SELECT MAX(Temp_VVB) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MIN(Temp_Ude) as Temperatur FROM pillestat_data_1 WHERE Temp_Ude = (SELECT MIN(Temp_Ude) FROM pillestat_data_1 LIMIT 1)
union all
SELECT DatoTid, MAX(Temp_Ude) as Temperatur FROM pillestat_data_1 WHERE Temp_Ude = (SELECT MAX(Temp_Ude) FROM pillestat_data_1 LIMIT 1)

它实际上只有18个查询，但需要很多时间。 300.000行的1.9866秒。

这300,000行只是一个小型数据库，预计会增加大约18,000万行。

我也试过这个

SELECT
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_FremL = (SELECT MIN(Modul_FremL) FROM pillestat_data_1 )) AS Min_DT_Temp1, MIN(Modul_FremL) AS Temp_Min_Temp1,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_FremL = (SELECT MAX(Modul_FremL) FROM pillestat_data_1 )) AS Max_DT_Temp1, MAX(Modul_FremL) AS Temp_Max_Temp1,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_ReturL = (SELECT MIN(Modul_ReturL) FROM pillestat_data_1 )) AS Min_DT_Temp2, MIN(Modul_ReturL) AS Temp_Min_Temp2,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_ReturL = (SELECT MAX(Modul_ReturL) FROM pillestat_data_1 )) AS Max_DT_Temp2, MAX(Modul_ReturL) AS Temp_Max_Temp2,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_Gas = (SELECT MIN(Modul_Gas) FROM pillestat_data_1 )) AS Min_DT_Temp3, MIN(Modul_Gas) AS Temp_Min_Temp3,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_Gas = (SELECT MAX(Modul_Gas) FROM pillestat_data_1 )) AS Max_DT_Temp3, MAX(Modul_Gas) AS Temp_Max_Temp3,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_FB = (SELECT MIN(Modul_FB) FROM pillestat_data_1 )) AS Min_DT_Temp4, MIN(Modul_FB) AS Temp_Min_Temp4,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_FB = (SELECT MAX(Modul_FB) FROM pillestat_data_1 )) AS Max_DT_Temp4, MAX(Modul_FB) AS Temp_Max_Temp4,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_SB = (SELECT MIN(Modul_SB) FROM pillestat_data_1 )) AS Min_DT_Temp5, MIN(Modul_SB) AS Temp_Min_Temp5,
(SELECT DatoTid FROM pillestat_data_1 WHERE Modul_SB = (SELECT MAX(Modul_SB) FROM pillestat_data_1 )) AS Max_DT_Temp5, MAX(Modul_SB) AS Temp_Max_Temp5,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_Kedel = (SELECT MIN(Temp_Kedel) FROM pillestat_data_1 )) AS Min_DT_Temp6, MIN(Temp_Kedel) AS Temp_Min_Temp6,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_Kedel = (SELECT MAX(Temp_Kedel) FROM pillestat_data_1 )) AS Max_DT_Temp6, MAX(Temp_Kedel) AS Temp_Max_Temp6,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_Central = (SELECT MIN(Temp_Central) FROM pillestat_data_1 )) AS Min_DT_Temp7, MIN(Temp_Central) AS Temp_Min_Temp7,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_Central = (SELECT MAX(Temp_Central) FROM pillestat_data_1 )) AS Max_DT_Temp7, MAX(Temp_Central) AS Temp_Max_Temp7,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_VVB = (SELECT MIN(Temp_VVB) FROM pillestat_data_1 )) AS Min_DT_Temp8, MIN(Temp_VVB) AS Temp_Min_Temp8,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_VVB = (SELECT MAX(Temp_VVB) FROM pillestat_data_1 )) AS Max_DT_Temp8, MAX(Temp_VVB) AS Temp_Max_Temp8,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_Ude = (SELECT MIN(Temp_Ude) FROM pillestat_data_1 )) AS Min_DT_Temp9, MIN(Temp_Ude) AS Temp_Min_Temp9,
(SELECT DatoTid FROM pillestat_data_1 WHERE Temp_Ude = (SELECT MAX(Temp_Ude) FROM pillestat_data_1 )) AS Max_DT_Temp9, MAX(Temp_Ude) AS Temp_Max_Temp9
FROM pillestat_data_1
LIMIT 1

但由于某种原因，它不适用于所有列。它适用于大约一半的列。

所以我希望这里有人可以帮助我优化我的代码。

// KIM

如果你想测试，那就制作了一个SQLFIDDLE。

http://sqlfiddle.com/#!9/2b1c8f/16

Answer 1

规范化的表格设计将是

devices table
-------------
id
name
...


temperatures table
------------------
id
user_id
datetime
device_id
temp

外键自动获取索引。如果您进行日期相关选择，还要为datetime列添加索引。

然后获取所有设备的最小和最大tmp

select d.name, min(t.temp) as minTemp, max(t.temp) as maxTemp
from temperratures t
join devices d on d.id = t.device_id
group by d.name

即使您有数百万条记录，也应该在几毫秒内返回结果。

MySQL - 如何从MIN / MAX值获取MIN / MAX日期

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